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(11) | EP 0 404 262 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Monoepoxide-polyol adducts, and process for preparing the same |
| (57) An adduct of:
a) one or more polyhydric alcohols of formula R(OH)n in which R or each R independently is an aliphatic or heterocyclic moiety of from 2 to 18 carbon atoms, the hydroxyl groups are attached to a primary carbon atom, or a secondary carbon atom with the proviso that there is a second hydroxyl group attached to a carbon atom no more than 4 carbon atoms away from said secondary carbon atom, and n or each n independently is an integer of from 2 to 6, and b) an at least equimolar amount of one or more monoepoxides of formula
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[0001] This invention relates to adducts of a polyhydric alcohol and a monoepoxide, and to a process for preparing the same. More particularly, the invention relates to a process for the preparation of an adduct of a polyhydric alcohol and an aromatic monoepoxide, to curable coating compositions containing such adducts, to a process for coating a surface by applying said composition and to the cured films obtained by this coating composition.
[0002] The resinous polyhydric polyether adducts are well-known useful materials in for example the solvent, foam and coating industry. They offer in general good properties, while being in coatings chemically more resistant than polyhydric polyester resins. For instance, GB-A-1,531,778 describes a preparation of "polyetheralcohols" used in the preparation of polyurethane foam by the addition of an epoxide (ethylene oxide, propylene oxide, or epichlorohydrin) to an at least divalent alcohol, such as glycerol or pentaerythritol, and polyethylene glycol e.g. for pharmaceutical use in the presence of alkaline catalysts.
[0003] Other examples for the preparation of these adducts are i.a. found in US-A-4,282,387, wherein the reaction of a monoepoxide (propylene oxide) and at least one active hydrogen containing compound is catalyzed by a calcium, barium or strontium containing catalyst; and US-A-4,326,047, wherein polyether hydroxyl-containing compounds (using propylene oxide) are prepared in the presence of a solid calcium naphthenate.
[0004] However, none of the above references addresses the desirability of preparing a monoepoxide-alcohol adduct having a relatively low viscosity (i.e., free of highly polymerized compounds) while containing a lesser amount of unreacted starting materials, in other words, a product with a narrow molecular weight distribution. In particular, the heretofore processes do not provide adducts of an aromatic monoepoxide and a polyhydric alcohol.
[0005] Accordingly, the present invention provides an adduct of:
a) one or more polyhydric alcohols of formula R(OH)n in which R or each R independently is an aliphatic or heterocyclic moiety of from 2 to 18 carbon atoms, the hydroxyl groups are attached to a primary carbon atom, or a secondary carbon atom with the proviso that there is a second hydroxyl group attached to a carbon atom no more than 4 carbon atoms away from said secondary carbon atom, and n or each n independently is an integer of from 2 to 6, and
b) an at least equimolar amount of one or more monoepoxides of formula
in which R′ or each R′ independently is an optionally substituted aromatic moiety
of up to 14 carbon atoms,
[0006] Mz and Mw are commonly used molecular weight averages obtained by different averaging methods referred to as "weight", and "z" and are based on ratios of successively higher moments of the molecular weight distribution.
[0007] Surprisingly, it was found that these adducts could be very advantageous to obtain and use in coating compositions, as they provide low viscosity resins in imparting hardness and resistance against most chemical compounds.
[0008] For high solids applications, a low concentration of free residual reactants and a narrow molecular weight distribution ranging from 1 to 1.15 is preferred, while a MWD ranging from 1 to 1.1 is even more preferred. The molecular weight distribution may be obtained by gel permeation chromatography as is known in the art.
[0009] The R′ moiety of the or each monoepoxide that is part of the adduct is an aromatic moiety, optionally containing hetero atoms, such as for instance phenyl, naphthyl, anthryl, pyridyl, furyl, and thienyl. More preferably, the R′ moiety is a phenyl, optionally bearing inert substituents, such as xylyl, mesityl, bromophenyl, chlorophenyl, or nitrophenyl. Most preferably the R′ moiety is phenyl.
[0010] Suitable polyhydric alcohols from which the adducts of the present invention may be obtained include low molecular weight polyols such as glycols, glycerines, modified sugars and starches, and tris(hydroxyalkyl)isocyanurates and the like.
[0011] Polyhydric alcohols in which the hydroxyl groups are attached to a secondary hydroxyl group whereas the nearest hydroxyl group is more than 4 carbon atoms away, as for instance 2,6-octylene glycol, are less suitable in that they show no or very little reactivity.
[0012] Particularly suitable glycols are any or more of for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,2-pentylene glycol, 1,3-pentylene glycol, 1,4-pentylene glycol, 1,5-pentylene glycol, and 2,2-dimethyl-1,3-propylene glycol and the like. Most suitable glycols are selected from any or more having the primary or secondary hydroxyl groups in beta or gamma position relative to each other, such as for instance ethylene glycol, 1,2- and 1,3-propylene glycol.
[0013] Particularly suitable low molecular weight polyols are selected from any or more of the isomers corresponding to tris(hydroxymethyl)ethane, -propane, -butane, -pentane, -hexane, -heptane, -octane, and -nonane; tetra(hydroxymethyl)methane, -ethane, -propane, -butane, -pentane, -hexane, -heptane, and -octane; penta(hydroxymethyl)ethane, -propane, -butane, -pentane, -hexane, and -heptane; and hexa(hydroxymethyl)ethane, -propane, -butane, -pentane, and -hexane.
[0014] Other particular suitable polyhydric alcohols are modified sugars and starches, i.e., those having more than one primary hydroxyl group, and heterocyclic compounds such as tris(hydroxyethyl)isocyanurate (THEIC) and the like.
[0015] Also particularly suitable are the dimers or ethylene oxide modified derivatives of the compounds above, with, however, the proviso that the total number of hydroxyl groups is up to 6, and the total number of carbon atoms is up to 18. It will be appreciated that the term "aliphatic polyhydric alcohol" as used throughout this application also includes aliphatic alcohols having one or more non-conjugated unsaturated links.
[0016] According to a preferred embodiment, the sole polyhydric alcohol or mixtures thereof are selected from primary polyhydric alcohols. In a more preferred embodiment the or each primary polyhydric alcohol is selected from ethylene glycol, 2,2-dimethyl-1,3-propanediol (i.e., neopentyl glycol or NPG), tris(hydroxymethyl)propane (i.e., trimethylolpropane or TMP), THEIC, or the dimer of TMP (DTMP). The most preferred primary polyhydric alcohol is TMP.
[0017] The present invention also provides for a process for preparing said adducts, which process comprises the contacting of:
a) one or more polyhydric alcohols of formula R(OH)n in which R or each R independently is an aliphatic or heterocyclic moiety of from 2 to 18 carbon atoms, the hydroxyl groups are attached to a primary carbon atom, or a secondary carbon atom with the proviso that there is a second hydroxyl group attached to a carbon atom no more that 4 carbon atoms away from said secondary carbon atom, and n or each n independently is an integer of from 2 to 6, and
b) an at least equimolar amount of one or more monoepoxides of formula
in which R′ or each R′ independently is an optionally substituted aromatic moiety
of up to 14 carbon atoms,
[0018] Surprisingly, it was found as result of extensive research and experimentation that by proper choice of the etherification catalyst, high yields of low viscosity well-defined adducts were obtained containing a lesser amount of both unreacted starting material and (highly) polymerized product in a most expedient manner, as is evident from the very narrow molecular weight distribution (MWD).
[0019] These selective etherification catalysts are known in the field of preparation of polyepoxy polyether resins (cf. EP-A-0,244,897), however, it was previously unknown that they provide both high selectivity and reactivity for the etherification of aromatic monoepoxides, such reactivity not being found in the case for e.g. aliphatic epoxides, and aliphatic and aromatic monoglycidyl ethers.
[0020] Suitable examples of etherification catalysts include halides, and salts of alkanoic and naphthenic acids, particularly of those having in the range of from 2 to 30 carbon atoms per molecule. Very suitable catalysts are tin, zinc or iron chlorides, tin or zinc alkanoates, dibutyltin dialkanoates, and iron salts of naphthenic acids. Preferred catalysts are tin(II)octoate, tin dichloride, dibutyltin dilaurate and tin tetrachloride, the former being most preferred.
[0021] The catalyst may be employed at relatively low concentrations and low reaction temperatures. Thus, addition of 0.01 to 0.5% m/m of catalyst while heating the reaction mixture to a temperature in the range of from 100 to 220 °C is adequate. Particularly suitable concentrations of catalyst range from 0.03 to 0.35% m/m, most suitably from 0.05 to 0.2% m/m. The reaction may very suitably be carried out at a temperature in the range of from 115 to 190 °C, preferably from 130 to 180 °C, most preferably from 150 to 175 °C.
[0022] Preferably, the relative amounts of starting materials a) and b) are such that the final adduct contains essentially no free starting alcohol at essentially complete conversion of the monoepoxide. Hence, the preferred relative amounts expressed in equivalents hydroxyl group per equivalent epoxy groups range from n to 0.8, more preferably of from (0.5n+0.6) to 1.1, most preferably of from 1.6 to 1.2, wherein "n" corresponds with the (average) number of hydroxyl groups in the (mixture of) polyhydric alcohol(s).
[0023] The adducts are very suitable for use in polyurethane resin preparation and high-performance automotive high solids top coatings. The latter coatings preferably further comprise one or more cross-linking resins, and little or no solvents. Also said coatings preferably comprise one or more catalysts, optionally together with an accelerator. Attractive cross-linking resins in the latter respect are for example those disclosed in European patent application No. 244,897. Particularly suitable cross-linking agents are the aminoplast-type resins, such as alkoxylated reaction products of formaldehyde with melamine or benzoguanamide. Other suitable cross-linking agents include urea-aldehyde resins, phenol-aldehyde resins, and blocked polyisocyanates. Suitable catalysts which may be employed in the curable coating compositions are acids such as orthophosphoric acid or p-toluenesulphonic acid. These catalysts may be used in a concentration range of from, for example, 0.05 to 2% by weight, calculated on polyether and cross-linking resin.
[0024] The relative proportions of adduct and cross-linking resin are those generally employed in the curable binders, typically of from 5 to 40% of cross-linking resin by weight, calculated on the total of adducts of the present invention and cross-linking resin.
[0025] The adducts of this invention are primarily intended to be employed in top coatings. Other applications such as in the preparation of polyurethanes, as solvents, or in the preparation of laminates or castings are also possible. The adducts may be blended with conventional solvents such as aliphatic or aromatic hydrocarbons, optionally being halogenated.
[0026] Pigments, fillers, dispersing agents and other auxiliary components known for coating formulations may be added to the curable binder system comprising the adducts made in accordance with the process of this invention.
[0027] The curable coating composition can be applied by a variety of methods as known in the art, for example by spraying, dipping, immersing or roller coating. The coatings can be cured by stoving, for example at temperatures from 75 to 300 °C, with curing temperatures varying from, for example, 10 seconds to 30 minutes.
[0028] The invention will be further illustrated by the following examples, however without restricting it's scope to these embodiments.
EXAMPLES
[0029] a) Experiments were carried out in a 1 litre glass reactor equipped with a stainless steel stirrer, nitrogen inlet, heating jacket, a thermocouple and a reflux condenser.
[0030] First, one of the alcohols below and styrene epoxide (PhEp) were charged into the reactor and homogenized by increasing gradually the temperature. When the system was homogenised, normally at about 100 °C, a catalyst was added. Then, the reactor was heated to the indicated reaction temperature. The reaction was followed by withdrawing samples at regular intervals and determining the decreasing epoxy group content (EGC) value. When 99% of the epoxide groups had reacted, the reaction was stopped by cooling. Experimental data are summarised in table 1.
| Name | Abbreviation | M.W. | H.F.* |
| Neopentyl glycol | NPG | 104 | 2 |
| Trimethylolpropane | TMP | 134 | 3 |
| Tris(hydroxyethyl)isocyanurate | THEIC | 261 | 3 |
| Di(trimethylolpropane) | DTMP | 250 | 4 |
| * H.F. is the hydroxyl functionality of the polyhydric alcohol. |
Table 1
| Intake (g) | Temp. (°C) | Time of reaction (h.) | MWD | free alc. %m/m | EGC meq/g | ||||
| alc. | PhEp | Sn(II) octoate | Mz/Mw | Mz | |||||
| TMP | 67 | 120 | 0.44 | 175 | 1.8 | 1.05 | 470 | 6 | 0.07 |
| NPG | 104 | 160 | 0.46 | 175 | 2.5 | 1.05 | 410 | 10 | 0.07 |
| THEIC | 111 | 102 | 0.48 | 175 | 8.0 | 1.07 | 470 | 6 | 0.08 |
| DTMP | 187 | 240 | 0.90 | 175 | 11.0 | 1.05 | 590 | 2 | 0.07 |
[0031] The adducts (except for the THEIC adduct) were further evaluated in coating formulations comprising the following compositions:
| Coating composition (80% solid content) | I (g) | II (g) |
| Adduct | 40.0 | 35.0 |
| Hexamethoxymethylmelamine, "HMMM" | 10.0 | 15.0 |
| Xylene | 12.5 | 12.5 |
| para-toluenesulphonic acid | 1.5 | 1.5 |
| (10% in butyl OXITOL; OXITOL is a registered trade mark) |
[0032] The clear lacquer was applied onto a bare steel panel in a dry film thickness of approximately 35 µm. The panel was stoved at a temperature of 140 °C for 30 minutes, after which the lacquer properties were assessed (table 2).
Table 2
| Alc. | Composition | Viscosity1) mPa.s | thickness (µm) | MEK (dbl. rubs) | Hardness2) (sec) |
| TMP | I | 35 | 40 | 183 | |
| II | 2740 | 35 | >100 | 178 | |
| DTMP | I | 38 | >100 | 190 | |
| II | 6030 | 35 | >100 | 180 | |
| NPG | I | 32 | >100 | 188 | |
| II | 546 | 35 | >100 | 136 |
| 1) Viscosity determined for a 90% solids composition. | |||||
| 2) König hardness determined using a Erichsen apparatus. |
1. An adduct of:
a) one or more polyhydric alcohols of formula R(OH)n in which R or each R independently is an aliphatic or heterocyclic moiety of from 2 to 18 carbon atoms, the hydroxyl groups are attached to a primary carbon atom, or a secondary carbon atom with the proviso that there is a second hydroxyl group attached to a carbon atom no more than 4 carbon atoms away from said secondary carbon atom, and n or each n independently is an integer of from 2 to 6, and
b) an at least equimolar amount of one or more monoepoxides of formula
in which R′ or each R′ independently is an optionally substituted aromatic moiety of up to 14 carbon atoms,
said adduct having a molecular weight distribution Mz/Mw of from 1 to 1.2.
a) one or more polyhydric alcohols of formula R(OH)n in which R or each R independently is an aliphatic or heterocyclic moiety of from 2 to 18 carbon atoms, the hydroxyl groups are attached to a primary carbon atom, or a secondary carbon atom with the proviso that there is a second hydroxyl group attached to a carbon atom no more than 4 carbon atoms away from said secondary carbon atom, and n or each n independently is an integer of from 2 to 6, and
b) an at least equimolar amount of one or more monoepoxides of formula
in which R′ or each R′ independently is an optionally substituted aromatic moiety of up to 14 carbon atoms,
said adduct having a molecular weight distribution Mz/Mw of from 1 to 1.2.
2. An adduct as claimed in claim 1, wherein the adduct has a molecular weight distribution
of from 1 to 1.15.
3. An adduct as claimed in claim 1, wherein the adduct has a molecular weight distribution
of from 1 to 1.1.
4. An adduct as claimed in any one of claims 1 to 3, wherein the R′ moiety is a phenyl
group, optionally bearing inert substituents.
5. An adduct as claimed in claim 4, wherein the R′ moiety is a phenyl group.
6. An adduct as claimed in any one of claims 1 to 5, wherein the or each polyhydric
alcohol is selected from glycols, low molecular weight polyols, glycerines, modified
sugars or starches, and tris(hydroxyalkyl) isocyanurates.
7. An adduct as claimed in claim 6, wherein the or each polyhydric alcohol is a primary
polyhydric alcohol.
8. An adduct as claimed in claim 7, wherein the primary polyhydric alcohol is selected
from ethylene glycol, neopentyl glycol, trimethylolpropane, di-trimethylolpropane,
or tris(hydroxyethyl)isocyanurate.
9. A process for preparing an adduct as claimed in any of claims 1 to 8, which process
comprises the contacting of a) one or more polyhydric alcohols of formula R(OH)n as heretofore defined, and b) an at least equimolar amount of one or more monoepoxides
of formula
as heretofore described, in the presence of an etherification catalyst selected from tin, zinc and iron compounds.
as heretofore described, in the presence of an etherification catalyst selected from tin, zinc and iron compounds.
10. A process as claimed in claim 9, wherein the relative amounts of polyhydric alcohol
and monoepoxide expressed in equivalents hydroxyl groups per equivalent epoxy groups
range from n to 0.8, n having the same meaning as in claim 1.
11. A process as claimed in claim 9, wherein the relative amounts range from (0.5n+0.6)
to 1.1.
12. A process as claimed in claim 1, wherein the etherification catalyst is selected
from chloride salts, tin or zinc alkanoates, dibutyltin(IV)alkanoates, and iron naphthenates.
13. A curable coating composition comprising an adduct as claimed in any of claims
1 to 8, and a cross-linking resin.